This invention relates to an image formation system such as copying machine and more particularly to a pressure developing unit of the image formation system for transferring and developing under pressure the image on a photosensitive and developing under pressure the image on a photosensitive and pressure-sensitive medium onto an image recording medium.
In the prior art, there is known a color copying machine in which a micro-capsule paper is exposed through an original, the micro-capsule paper being a photosensitive and pressure-sensitive medium having a surface on which is carried a micro-capsule including a color precursor and a photopolymerization initiator and having a mechanical strength which is varied in response to the light. The exposed micro-capsule paper and a developer paper as an image recording medium prepared by sticking a granular developer by a developer coating device on a surface of a carrier member such as an ordinal paper are fed into a pressure developing apparatus in which the exposed micro-capsule paper and the developer paper are tightly contacted under pressure. The micro-capsule having a weak mechanical strength is broken by the pressure, resulting in the flow-out of the color precursor contained in the micro-capsule, the flown precursor and the developer are reacted. In such manner, the developed color image is transferred on the developer paper and the developer paper after the pressure developing operation is fed to a heat fixing device to fix the color image on the developer paper.
The pressure developing apparatus of the character described above is usually composed of a plurality of rollers arranged to be rotatable about their rotation axes which are parallel with each other. A various kind of means for applying pressure to the rollers are well known.
One of known pressure applying means is of the type in which a large diameter roller having a high rigidity is utilized and such pressure developing apparatus is disclosed in the Japanese Patent Laid-Open Publication No. 63-262650.
Another one of known pressure applying means is of the type in which a small diameter roller having a low rigidity is supported at multiple points on a large diameter roller having a high rigidity and such pressure developing apparatus is disclosed in the U.S. Pat. No. 4,104,963.
In the pressure developing apparatus, in a case where a pressure is applied unevenly along the direction of the rotation axis of the roller, the paper to be developed may be crinkled or the paper may be unevenly developed. For this reason, in the former known pressure applying means, is utilized a roller of a shape having curvature directed in the rotation axis, or the rotation axes of the pressurizing roller and the pressurized roller are offset so as not to be parallel and the adjustment is carried out in accordance with the crossing angle therebetween. Furthermore, in the later known pressure applying means, pressures at the respective pressurizing points are adjusted by means of coil springs.
However, in the pressure distribution adjustment in the described known pressure developing apparatus, working processes of the complicated parts involve the increase of working cost, assembling cost and so on. The increasing of the constructional parts may result in high possibility of generation of accident and in an inadequate performance of the desired operations due to errors in manufacturing or working the same.
Furthermore, in another aspect, there is proposed a pressure developing apparatus in which the pressure application and distribution are adjusted by changing the paper supporting positions of the roller in accordance with the size of the papers such as A4 size (210.times.297 mm) or B5 size (182.times.257 mm). However, in such type pressure developing apparatus, the pressure distribution adjustment requires much time and labor, thus being inconvenient.